In recent years, a carbon fiber-reinforced resin composition has been valuated as exhibiting excellent mechanical properties such as strength and rigidity in spite of its low specific gravity, and has drawn attention as an industrially important material. Particularly, in automobile components and aircraft components, a shaped product of a resin composition which is obtained by reinforcing with a carbon fiber a polyolefin resin excellent in rigidity and advantageous also in recycling property and high speed moldability has been drawing attention as alternative materials for metal materials and glass fiber-reinforced resin compositions. However, the shaped product has not become sufficiently popular as an alternative product for metal materials and glass fiber-reinforced resin compositions. The cause of this is that since a polyolefin resin is non-polar, its interface adhesion with the carbon fiber is poor and the carbon fiber cannot manifest the sufficient reinforcing effect, or since the carbon fiber itself is manufactured through a large amount of energy and a complicated manufacturing process, the shaped product is still expensive.
In order to improve interface adhesion between the polyolefin resin and the carbon fiber, for example, a method of adding an acid-modified polyolefin resin to a matrix resin (Patent document 1, for example), a method of adding a polyamide resin in addition to an acid-modified polyolefin resin (Patent document 2, for example), and a method of adding an acid-modified polyolefin resin and an amino group-containing modified polyolefin resin (Patent documents 3 and 4, for example) have been disclosed. However, in any method, the content of an expensive carbon fiber relative to the whole composition is high, or when the polyamide resin is used concurrently, the large amount of carbon fiber must be used for exhibiting strength under the conventional technical level and saving of the use amount of these materials is demanded. In addition, also in respect of strength, further improvement is demanded in the field of automobile and aircraft components.